Cooling fans



Nov. 30, 1965 ELMER 3,220,484

COOLING FANS Filed March 30, 1964 5 SheetsSheet 1 INVE N-roR Akflluz E. H. fLMEK BY v I ATTORNEB Nov. 30, 1965 A. E. H. ELMER COOLING FANS 5 Sheets-Sheet 2 Filed March 30, 1964 INVENTOR ARfl/ug 21H Ems/ A-r TORNEYS Nov. 30, 1965 A. E. H. ELMER 3,220,484

COOLING FANS Filed March 30, 1964 5 Sheets-Sheet 3 INVENTOR AF Hv/Z EH ELM EA ATTORNEY 8 Nov. 30, 1965 A. E. H. ELMER COOLING FANS 5 Sheets-Sheet 4 Filed March 30, 1964 m m E V N 1 A rro/e/vrs Nov. 30, 1965 A. H. ELMER 3,220,484

COOLING FANS Filed March 30, 1964 5 Sheets-S heet 5 1 NVEN T OR. Aer/we E. 51/ 458 United States Patent 3,220,484 COOLING FANS Arthur E. H. Elmer, Painswick, England, assignor to Dowty Hydraulic Units Limited, Cheltenham, England, a British company Filed Mar. 30, 1964, Ser. No. 355,768 Claims priority, application Great Britain, Apr, 11, 1963, 14.621, 14,622; Jan. 2, 1964, 251 22 Claims. (Cl. 170-16053) This invention relates to cooling fans suitable for use in a vehicle for cooling the engine of the vehicle.

According to the invention a cooling fan, suitable for use in a vehicle, and arranged to be driven by the engine of the vehicle, has blades each of whose pitch is adjustable automatically during operation bodily about a pitchchange axis directed generally radially, in response to changes in its rotational speed about the fans rotational axis, to maintain the volume of air passing through the fan substantially constant throughout a large proportion at least of the operational rotational speed range of the fan.

According to a primary feature of the invention the blades of the cooling fan are capable of bodily movement from coarse pitch towards fine pitch under centrifugal twisting moments about their radial axes (which increase with increase in rotational speed), which twisting moments are inherent in the blades during rotation of the fan, and which are distinct from the force properly termed the centrifugal force of the fan as a whole, such moments being reacted by spring means.

The spring means may comprise radially-directed torsion bars or springs arranged either within or alongside the blades, being anchored at their radially-inner end portions to the hub of the fan in which or upon which the blades are mounted, and at their radially-outer end portions being each anchored at a suitable position along the length of the respective blade. The root end portions of the blades may be plugged into or supported upon locating members formed in or carried upon the hub with freedom for pitch change movement of the blades about their longitudinal that is to say, their radially directed pitch change axes, the torsion bars or springs serving also as retaining means in the radial sense for the blades with respect to the hub.

The torsion bars or springs may be of double-looped form.

Stop means may be provided between the root of each blade and its locating member in or on the hub to limit the extent of movement of the blade in the coarse pitch and fine pitch directions, this stop means also serving to limit, or in essence to prevent, radial-outward displacement of each blade. The stop means may act to limit undesirably high tensile loading of the torsion bars or springs under relatively high centrifugal loading such as encountered during any overspeed operating condition of the fan.

Also, according to the invention, the blades of the cooling fan additionally may be adjustable, each about its pitch-change axis, automatically during operation by thermo responsive means, such adjustment being in response to changes in the temperature of the air entering the fan after having passed in heat-exchange relation with the engine, this adjustment modifying the adjustment occurring under the centrifugal twisting moments. Thus by the provision of adjustability in response to temperature, the fan is enabled to operate within a predetermined temperature range.

The thermo-responsive means may include one or more capsule-type thermostats.

The thermo-responsive means may be connected to the blades so that pitch change of these blades under the control of these means occurs in unison.

ice

The operation of the thermo-responsive means may be reacted, at least in part, by the same spring means as react the centrifugal twisting moments.

The operation of the thermo-responsive means may be further reacted by supplementary spring means interposed in the connections between the thermo-responsive means and the blades.

The thermo-responsive means may be secured to the hub of the fan and may include a heat sink member arranged in heat conducting relation with the air which in operation passes through the fan. The heat sink member is preferably provided with a high surface area to low material volume to afford relatively rapid operation of the thermo-responsive means. 7

Under control by the thermo-responsive means the blades of the fan may be moved in the pitch coarsening sense with increase in temperature.

According to yet a further feature of the invention, the cooling fan may also include a device co-operable with the said stop means and displaceable from a first position to at least a second position thereby to afford at least two minimum and/ or two maximum selective pitch settings. In this way the device is adjustable at will so that the minimum and/ or maximum pitch settings of the fan can be selected in accordance with the ambient, temperature con ditions under which the fan is required to operate, such for example as correspond to winter and to summer operation. I p

The hub of the cooling fan may comprise at least two complementary pressings secured together and shaped so as to provide locating means for the blades of the fan,

but locating means which have the lowest possible hys teresis losses, from friction, etc.

Again, the blades of the fan may each comprise at least two complementary pressings secured together and shaped in a manner such that the blade can be fitted onto or into the hub of the fan.

The complementary pressings of the hub may, as with those also of each blade, be secured together at least in part by rivet or like means which provide, or assist in,

providing, anchorage for said radially-directed torsion bars or springs.

Five embodiments of the invention will now be par.- ticularly described, by way of example, with reference to the accompanying drawings, of which,

FIGURE 1 is a perspective view of a four-bladed automatically variable pitch cooling fan for the engine of a vehicle, a

FIGURE 2 is a partly cut-away view of one blade of the fan shown in FIGURE 1, taken in the direction of the arrow II,

FIGURE 3 is a partly cut-away view of the blade shown in FIGURE 2 and of a part of the fan hub, taken upon FIGURE 1 in the direction of the arrow 111,

FIGURE 4 is a perspective view of a four-bladed thermo-responsive fan forming the second embodiment of the invention,

FIGURE 5 is a partly cut-away view of part of a blade and of the hub of a fan forming the third embodiment of the invention, and incorporating means for adjusting its setting for summer and for winter operation.

FIGURE 6 is a partly cut-away view of part of a blade and of the hub of a fan forming a fourth embodiment of the invention, and,

FIGURE 7 is a partly cut-away view of part of a blade and of the hub of a fan forming a fifth embodiment of the invention.

FIGURE 8 is a series of diagrams illustrating the source of the centrifugal twisting moments acting upon each fan blade during rotation of the fan, and the result thereof, such as tends to move each blade towards its fine pitch position with increase in the fans rotational speed.

3 Referring to FIGURES 1, 2 and 3 of the drawings, a four-bladed cooling fan 11 suitable for use in a road vehicle for cooling the engine of the vehicle comprises a hub 12 which can be attached to a pulley (not shown) mounted so that it may be driven by'the engine at a speed corresponding to the engines speed, through a belt or other suitable means. The hub is attached to the pulley by means of set bolts (not shown) which are passed through the four holes 13 provided in the hub.

The hub comprises two steel pressings 14 and 15, these pressings being of such shape that when they are secured together by four rivets 16 they define a hub with four radially-outwardly directed tubular projections 17. These projections each carry a blade 18 in a manner hereinafter described, each blade being angularly adjustable as to pitch with respect to its tubular projection 17 and about its longitudinal pitch change axis. Each blade comprises a sheet metal working portion 19 of suitable and substantially unchanging camber and a portion 20 which is spot-welded to the portion 19 and shaped so as with the portion 19 to define a root socket whereby the blade is mountable upon its tubular projection 17 with the desired amount of clearance for pitch change movement.

With particular reference to FIGURE 2, each tubular projection 17 is provided with a pair of slots, one of which is shown at 21, stop means in the form of a pin 22 secured to the blade root passing through these slots. Thus the pin 22 in association with slots 21 limits the range of pitch change adjustment of its associated blade 18.

With reference to FIGURE 3 of the drawings for each blade 18 a double-looped torsion spring 23 is anchored at its radially-inner end portion to the associated rivet 16, and thus to the hub 12, while at-its radially-outer end portion this spring is anchored upon engaging portions 24 and 25 of the pressings of the working portion 19 and the portion 20 respectively. A rivet 26 passes through the aperture 27 defined by the portions 24 and 25 to provide a firmanchorage for the outer end portion of the torsion spring.

In addition to operating as means for limiting the pitch change range of the blades, each pin 22 in association with itsv slots 21 forms a safety stop for its blade 18 in case of fracture of the torsion spring 23. Accordingly there is a clearance of the order of .060 inch between the diameter of each pin and the width of the slots, to limit to the greatest degree frictional resistance to pitch change, and yet capable of acting so that if a spring fractures the pin will engage the radially outer side of its slot so that the blade cannot come adrift from the hub. In diagrammatical.FIGURE 8 the views I, II, III, show the geometrical position of a blade turned at an angle T from the plane of rotation when fan rotation is about the y axis. The forces then acting are represented by the arrows aA, 1113, where A and B are the centres of inertia of each half of the blade. These forces can be analysed into components of which the sum of those two (CF and CF) acting parallel to the z axis (the longitudinal pitch change axis of the blade) is commonly called the centrifugal force, while those (TM and TM) acting parallel to the x axis form a couple acting about the z axis and tending to reduce the angle T. This couple is commonly called the centrifugal twisting moment and is proportional to the product of the mass of the blade, the square of the radius of gyration of the blade about the z axis, the square of the fan rotational speed, and also the sine of twice the angle T.

In FIGURE 8 (IV) these forces are shown in perspective.

In operation of the fan at low engine rotational speeds, the blades, 18 are at a relatively coarse pitch condition, but as the speed of the engine increases, the centrifugal twisting moments about the radial pitch-change axis, inherent in the blades, also increase in a manner such that the blades move in the pitch fining direction against the efiort of the torsion springs 23.

At relatively slow speed operation, with coarse blade pitch, the fan passes a given volume of air for cooling purposes. As the speed of the fan increases, had the pitch of the fan blades remained the same, an increasing volume of air would have been passed. However, the automatic reduction in the pitch afforded by the inherent centrifugal twisting moments reacted by the torsion springs is such that the volume of air passed by the fan is maintained substantially constant. Such substantially constant volume of air is determined by the blade area, the characteristics of the torsion springs and the speed range within which the fan is required to operate.

By so controlling the volume of air passing through the fan, the horse power absorbed by the fan throughout its operational speed range increases by only a small amount from a low rotational speed condition to the high rotational speed condition as compared with the relatively larger power absorption by the fan occurring with fans of fixed pitch over a similar operational speed range.

Although the blades 18 are anchored with respect to the hub 12 by the torsion springs 23, as the centrifugal force acting upon the blades increases with increase in speed of the fan, stretching of the torsion springs occurs to a small extent, of the order of .005 inch to .010 inch, this being permitted by the clearance between each pin 22 and its slots 21.

By virtue of the fact that the torsion springs 23 not only provide means for reacting the centrifugal twisting moments but also provide blade retaining means in the radial sense, very low bearing friction is evident in the fan and thus sensitive response in pitch change operation is afforded. The presence of clearance between each pin 22 and its slots 21 prevents frictional resistance to centrifugal twisting moments, which are small as compared to the centrifugal force upon the blade as a whole.

By virtue of the looping of the torsion spring a double wire spring element of required characteristics is provided for each blade.

The fan hereinbefore described is advantageous over fixed pitch fans of conventional type in that with the latter the relatively high power absorbed towards the higher speeds of operation of the fan are in excess of what is only actually necessary to satisfy the cooling demands of the engine. Therefore the present invention ensures that such increase in power absorbed is reducedto amarked extent as to have some advantageous effect in the economy of operation of the associated engine.

Further, some reduction at least in noise level is advantageously achieved because of the lower power absorption at the higher engine operating speed.

Where a fan in accordance with the invention is used in a relatively high speed vehicle, the ram air effect upon the fan would be taken into account, to a certain degree at least, in determining the characteristics of the torsion springs for the desired substantially constant air volume passing through the fan for the cooling of the engine.

In a slightly modified form of the construction of FIG- URJES 1, 2 and 3, the dimensions of the slots and pins and the characteristics of the torsion springs are instead chosen such that. if any undesirable overspeeding condition is encountered the torsion springs will not be subjected to resultant excessive high tensile loading, but this loading will be imposed directly through each pin 22 onto the radially-outer side of each slot 21 and thus onto the hub 12. Thus no overstressing of the torsion springs is allowed to occur, nor is there any appreciable radiallyoutward movement of the blades due to centrifugal force or any other force.

Referring now to FIGURE 4 of the drawings, there is shown a cooling fan'for the engine of a vehicle which basically is similar in construction to that of FIGURES 1, 2 and 3. However, this fan is provided with temperature-responsive means generally indicated at 31, so that the blade pitch angle adjustment is not only dependent upon the centrifugal twisting moments inherent in the blades themselves, but is also dependent upon the temperature of the air passing through the fan.

Since, however, this fan is basically similar to that of FIGURES 1, 2 and 3 the same numerals are applied for equivalent components.

The temperature-responsive means includes a heat sink member in the form of a disc 32 having a series of radially-directed forwardly extending fins 33. This disc is rigidly secured by set bolts 34 to the forward face of the hub 12 of the fan, and these bolts may serve also to mount the fan upon its associated pulley (not shown). The disc 32 is spaced somewhat forwardly of the hub 12 by spacer members 35, carried by the set bolts 34. A second disc 36, which is partly shown in the drawing through the cut-away portion to the disc 32, is so mounted with respect to the spacer members 35 as to be capable of limited angular adjustment about the rotational axis of the fan and with respect to the disc 32, suitable elongated slots 37 being provided for this purpose. The second disc 36 is provided with four apertures, one of which is shown at 38, and the stop pins 22 fixed to the roots of the blades are longer than those of the construction of FIGURES 1, 2 and 3, extending forwardly each to engage an aperture 38.

The second disc 36 is cut-away at two diametricallyopposed portions, one of which is shown at 39 in the drawing.

The rearward face of the disc 32 carries two wax capsule-type thermostats one of which is shown at 40. The plungers 41 of the two thermostats are respectively in engagement through the intermediary of leaf springs, only one of which is shown at 42, with radial faces 43 (again only one of which is shown) formed by the cutaway portions 39 of the second disc 36.

Thus the heat sink member or disc 32 is positioned in heat conducting relationship with respect to the two capsule-type thermostats 40 and as the temperature of the air passing through the fan increases the heat sink member transmits this to the thermostats and in consequence the plungers 41 are extended to cause angular displacement of the second disc 36 about the rotational axis of the fan. Since the disc 36 is connected to the extended pins 22 this movement of the member causes pitch coarsening movement of the blades 18 in unison.

In operation of the fan at low engine rotational speeds the blades are at a relatively coarse pitch condition, but as the speed of the engine increases the centrifugal twisting moments inherent in the blades increase as described with reference to FIGURES 1, 2 and 3 in a manner such that the blades move in the pitch fining direction against the effort of the torsion springs within the blades.

Before entering the fan, air for cooling of the engine passes through a conventional water radiator forming part of the engine installation. Thus, the air so passing in heat-exchange relation with the engine absorbs heat to an extent dependent upon the engine operating temperature. When this air attains a predetermined temperature, the wax-capsule-type thermostats 40 are operable to rotate the second disc 36 for pitch coarsening adjustment of the blades. The arrangement is such that the pitch coarsening, which is subtractive upon the adjustment of pitch under centrifugal twisting moments in the fine direction, takes place at approximately degrees Fahrenheit above the set thermostat operating temperature. As the fan blades move into their coarser pitch condition the air flow is appropriately increased to afford additional cooling effects required such as may be necessary when the vehicle is operating in slow heavy trafiic conditions with frequent stops.

When the rotational speed of the fan thereafter increases, the left springs 42 afford sufficient resilience in the connection between thermostats and blades as to permit the blades then to move in the pitch fining direction proportional to rotational speed, the displacement of the thermostats thus having now however raised the rotational speed condition at which such pitch fining commences.

Thus, with the fan shown in FIGURE 4, at relatively slow rotational speed operation, with coarse blade pitch, the fan passes a given volume of air for cooling purposes. As the speed of the fan increases, with increase in engine speed, had the pitch of the fan remained the same, an increasing volume of air would have passed. However, the automatic reduction in pitch afforded by the inherent centrifugal twisting moments reacted by the torsion springs is such as to maintain, during normal running of the vehicle, a substantially constant volume of air passing through the fan. However, under very slow running conditions, for example, when there is a tendency for the engine to overheat, the thermo-responsive means is operable to maintain operation of the engine substantially within a predetermined temperature range.

By so controlling the volume of air passing through the fan, the horse power absorbed by the fan throughout its operational speed range increases by only a small amount from the low rotational speed condition to the high rotational speed condition as compared with the relatively larger power absorption by the fan occurring with fans of fixed pitch over a similar operational speed range.

With reference to FIGURE 5 of the drawings, this shows part of the hub and a blade of a fan similar in construction to that of FIGURES 1, 2 and 3. This fan however differs in that a device is provided which affords two minimum selective pitch settings for the blades 18.

The device comprises a disc member 50 mounted upon a spigot 51 projecting forwardly from the hub 12 of the fan. This member is provided with four radially-outwardly-directed projections, one for each blade, one such projection being shown in the drawing at 52.

Each projection 52 is co-operable with the stop pin 22 of the respective blade. As with the construction of FIGURE 4, the stop pin 22 is extended forwardly and externally of the blade root as shown.

Mounted in the hub is a spring-loaded pin device 53, the spring 54 thereof normally urging the pin 55 forwardly to project from the hub 12 and to engage either one or the other of two apertures 56 and 57 formed in the disc member 50. In this way the disc member can be fixed in either of two angular positions depending upon which of the apertures 56 or 57 the pin 55 engages. In its first position, with the pin engaged in the aperture 56, the radially-outwardly directed projections 52 are so positioned clear of the blade root pins 22 that in operation of the fan the blades are permitted to move through the pitch change range predetermined by the full length of the slots 21 in the tubular projections 17. This corresponds to a winter operation setting of the fan where a larger pitch change range is required than, in summer.

When the member 50 is angularly adjusted to its second position by depressing the pin 55 out of engagement with the aperture 56, and turning the member 50 until the pin 55 springs into the aperture 57, the fan is then in its summer setting. Here the radially-outwardly directed projections 52 are positioned in relation to the slots 21 in the tubular projections 17 so that movement of the blades 18 in the pitch fining direction is limited because the pins 22 are no longer permitted to move fully to the fine pitch end portions of the slots 21, but instead are arrested in their movement by the projections 52 at a blade angle which is approximately 18 degrees higher than the minimum fine pitch angle appropriate to the winter setting.

By the provision of the disc member 50, a relatively high minimum fine pitch setting of 35 degrees for summer operation is afforded, giving excess cooling under high engine rotational speeds. For operation at the winter setting the blades are allowed to fine off to 17 degrees,

in this way the summer excess cooling no longer being provided because the blades move to their minimum fine pitch setting determined by the full length of the slots 21.

Although it is a relatively straightforward matter, when necessary, by simple depression of the pin 55 and angular movement of the disc member 50 upon its spigot 51 to change from winter setting to summer setting or vice versa, the invention is in no way limited to this means of adjustment. In other embodiments of the invention, adjustment is achieved by the provision of suitable presetting cam means or the like easily accessible to the operator of the vehicle in which the fan is installed.

Further, although in the above-described embodiment, only two settings are provided, in alternative embodiments of the invention, more than two settings are provided, this where the vehicle in which the fan is installed, is required to operate in zones Where ambient temperatures are widely varying.

Further, although in the embodiment described above with reference to FIGURE the adjustment in pitch change range has been applied to fine pitch settings, in another embodiment of the invention as shown in FIG- URE 6 the adjustment in the setting is instead applied at the coarse pitch end of the pitch change range, each projection 62 being co-operable with the stop pin 22 of the respective blade 18 in a manner similar to that shown in FIGURE 5, but in the sense to limit movement of the blade towards coarse pitch.

Again, in another alternative embodiment of the invention as shown in FIGURE 7, in addition to the disc member 50 described in the third embodiment above, a further similar and independently adjustable disc member 70 is provided, having projections '72, one associated with each blade pin 22, for adjustment in the pitch setting at the coarse pitch end of the pitch change range. Themember 50 is provided with an arcuate slot 73 whereby the spring-loaded pin 55 can pass through this member to engage either of the apertures 56 or- 57. A further spring-loaded pin 74 is provided in the hub 12, this pin being engageable with either of the apertures 75 or 76 in the disc member 70. Thus by virtue of these two independently and relatively displaceable members 50 and 7 0, the blades are aiforded two minimum and two maximum selective pitch settings.

In yet a further alternative embodiment of the invention, the arrangement of disc member is similar to that in the first above described embodiment but the disc member is further angularly adjustable so that the radiallyoutwardly-directed projections can alternatively be utilised for change in the pitch settings at the coarse pitch end of the pitch change range. This arrangement is such that for changeover from effectiveness upon fine pitch to effectiveness upon coarse pitch, each projection is displaced so that it moves from the fine pitch end of the slot 21 of one blade around tothe coarse pitch end of the slot 21 of an adjacent blade. In this way each projection has predetermined settings in association with one blade for fine pitch setting adjustability and predetermined settings in association with an adjacent blade for coarse pitch setting adjustability.

Although in all the embodiments described on the basis of the drawings reference has been made to the appication of the invention to the engine of a vehicle, the invention may also be applied with advantage to engines of fixed installations.

- Further, although in the embodiments described with reference to the drawings the fans have been provided with four blades, the invention is in no way limited to such number as in other embodiments any desired number of blades may be used.

Again, although in the embodiments described with reference to the drawings, the blades are formed with sockets whereby they are mounted upon radially-outwardly-extending projections from the hub, the invention '8 is in no way limited to this construction as in other embodiments of the invention the blades themselves may have tubular or like root portions, which are mounted in socket portions formed in thehub.

In other further embodiments, instead of the hub being formed as two pressings secured together, it is of other suitable structure, for example machined from solid, and where radially-outwardly extending projections are provided these are separate parts, for example welded or otherwise secured to the hub.

I claim as my invention:

1. A cooling fan for use in cooling a variable speed engine, and operable automatically to maintain the volume of air passing through the fan substantially constant throughout a large part at least of the operational speed range of the fan, said fan comprising in combination:

(a) A hub mounted for rotation by such engine about a rotational axis, at a speed that varies in accordance with the speed of such engine,

(b) blades mounted upon said hub for bodily rotation each about an axis directed substantially radially of the rotational axis, such blade rotation being arranged to occur automatically from coarse pitch towards fine pitch with increase in rotational speed of the fan, under the influence of centrifugal twisting moments about the blades radially directed axes, which moments are inherent in each blade during rotation of the fan about its rotational axis, and

(c) torsion springs directed generally radially, at least one for each blade, opposing such centrifugal twisting moments and active to rotate the blades back towards coarse pitch upon decrease in rotational speed of the fan.

2. A cooling fan as in claim 1, whereinthe mass of each blade is disposed substantially equally at the opposite sides of its radial axis.

3. A cooling fan as claimed in claim 1, wherein the torsion springs are anchored at their radially-inner end portions to the hub of the fan, and at their radially-outer end portions are each anchored to the corresponding blade at a suitable position along the length of such blade. 4. A cooling fan as claimed in claim 3, wherein the root end portions of the blades and the hub are complementally formed to support and locate the blades upon the hub, with freedom for pitch change movement of the blades about their radially directed pitch change axes.

5. A cooling fan as claimed in claim 4, wherein the torsion springs serve also as retaining means in the radial sense for the blades with respect to the hub.

6. A cooling fan as claimed in claim 1, wherein the torsion springs are of double-looped form.

7. A cooling fan as claimed in claim 4, wherein stop means are provided between the root of each blade and its locating member on the hub to limit the extent of movement of the blade in the coarse pitch and fine pitch direction.

8. A cooling fan as claimed in claim 7, wherein the stop means are arranged to serve also to limit radial-outward displacement of each blade.

9. A cooling fan as claimed in claim 1, including thermo responsive means reacting between the blades and the hub to effect automatic adjustment of the blades in response to changes in the temperature of air entering the fan after having passed in heat-exchange relation with the engine, this adjustment modifying the adjustment occurring under the centrifugal twisting moments.

10. A cooling fan as claimed in claim 9, wherein the thermo-responsive means includes at least one wax-capsule type thermostat.

11. A cooling fan as claimed in claim 9, wherein the thermo-responsive means are connected to the blades so that pitch change of the blades under the control of these means occurs in unison.

12. A cooling fan as claimed in claim 9, wherein the operation of the thermo-responsive means is, at least in part, reacted by the same spring means as react the centrifugal twisting moments.

13. A cooling fan as claimed in claim 12, wherein the operation of the thermo-responsive means is further reacted by supplementary spring means interposed in the connections between the thermo-responsive means and the blades.

14. A cooling fan as claimed in claim 9, wherein the thermo-responsive means are secured to the hub and include a heat sink member arranged in heat conducting relation with the air which in operation passes through the fan.

15. A cooling fan as claimed in claim 14, wherein the heat sink member is provided with a high surface area to low material volume to afford relatively rapid operation of the thermo-responsive means.

16. A cooling fan as claimed in claim 7, further including a device co-operable with the said stop means and displaceable from a first position to at least a second position thereby to afford at least two minimum selective pitch settings.

17. A cooling fan as claimed in claim 7, further including a device co-operable with the said stop means and displaceable from a first position to at least a second position thereby to afford at least two maximum selective pitch settings.

18. A cooling fan as claimed in claim 7, further including a pair of devices co-Operable with the said stop means and both independently and relatively displaceable from a first position to at least a second position thereby to aiford at least two minimum and two maximum selective pitch settings.

19. A cooling fan as claimed in claim 1, wherein the hub comprises at least two complementary pressings, se-

10 cured together and shaped as then to provide locating means for the blades of the fan.

20. A cooling fan as claimed in claim 1, wherein each blade comprises at least two complementary pressings secured together and shaped in a manner such that the blade can be fitted onto the hub of the fan.

21. A cooling fan as claimed in claim 19, wherein the complementary pressings are secured together at least in part by rivet or like means which at least assist in pro viding anchorage for said radially-directed torsion springs.

22. A cooling fan as claimed in claim 20, wherein the complementary pressings are secured together at least in part by rivet or like means which at least assist in providing anchorage for said radially-directed torsion springs.

References (litetl by the Examiner UNITED STATES PATENTS 546,630 9/1895 Tuerk 170160.61 1,489,841 4/1924 MacDonald 12341.49 2,149,267 3/1939 Bouvy et a1. 170-160.5 2,440,519 4/1948 Mooney l160.13 2,452,444 10/1948 Enerud 160.53 2,988,156 6/1961 Coleman 170160.53 3,096,827 7/1963 Woods 170-16013 3,096,828 7/1963 Hollingsworth 170160.14

FOREIGN PATENTS 568,951 1/1924 France. 867,965 5/ 1961 Great Britain.

SAMUEL LEVINE, Primary Examiner.

EDGAR W. GEOGHEGAN, JULIUS E. WEST,

Examiners. 

1. A COOLING FAN FOR USE IN COOLING A VARIABLE SPEED ENGINE, AND OPERABLE AUTOMATICALLY TO MAINTAIN THE VOLUME OF AIR PASSING THROUGH THE FAN SUBSTANTIALLY CONSTANT THROUGHOUT A LARGE PART AT LEAST OF THE OPERATIONAL SPEED RANGE OF THE FAN, SAID FAN COMPRISING IN COMBINATION: (A) A HUB MOUNTED FOR ROTATION BY SUCH ENGINE ABOUT A ROTATIONAL AXIS, AT A SPEED THAT VARIES IN ACCORDANCE WITH THE SPEED OF SUCH ENGINE, (B) BLADES MOUNTED UPON SAID HUB FOR BODILY ROTATION EACH ABOUT AN AXIS DIRECTED SUBSTANTIALLY RADIALLY OF THE ROTATIONAL AXIS, SUCH BLADE ROTATION BEING ARRANGED TO OCCUR AUTOMATICALLY FROM COARSE PITCH TOWARDS FINE PITCH WITH INCREASE IN ROTATIONAL SPEED OF THE FAN, UNDER THE INFLUENCE OF CENTRIFUGAL TWISTING MOMENTS ABOUT THE BLADES'' RADIALLY DIRECTED AXES, WHICH MOMENTS ARE INHERENT IN EACH BLADE DURING ROTATION OF THE FAN ABOUT ITS ROTATIONAL AXIS, AND (C) TORSION SPRINGS DIRECTED GENERALLY RADIALLY, AT LEAST ONE FOR EACH BLADE, OPPOSING SUCH CENTRIFUGAL TWISTING MOMENTS AND ACTIVE TO ROTATE THE BLADES BACK TOWARDS COARSE PITCH UPON DECREASE IN ROTATIONAL SPEED OF THE FAN. 